1. Field of the Invention
The present invention is related to cotton gins. More particularly, the present invention relates to a method and apparatus for increasing the moisture content of cotton during a cotton ginning process.
2. Description of the Related Art
Since it was invented by Eli Whitney more than a century ago, the cotton gin has remained the primary tool used to remove extraneous material, more commonly known as "trash," from newly-picked cotton. The "trash" removed typically includes seeds and other parts of the cotton plant that are collected together with the raw cotton when it is harvested. This "trash" must be separated from the cotton fibers before the fibers can be processed into thread and, ultimately, into fabric.
Cotton, however, is not ginned immediately after it is picked. Instead, among other pre-ginning processes, high moisture seed cotton is first partially dried in various types of apparatus known as a tower dryer or a seed cotton dryer of some other type. The tower dryer is a direct application of the knowledge that cotton is more easily ginned when it has a low moisture content.
To dry cotton, the conventional tower dryer includes a vertical tower casing, with substantially parallel shelf partitions. These shelf partitions alternately extend from one end wall of the tower casing to a location near the opposite end wall. So configured, the shelf partitions define a continuous zig-zag passage through the tower casing that guarantees a sufficient amount of drying by ensuring that the cotton remains in the dryer for a selected period of time at a desired temperature or range of temperatures.
In the conventional seed cotton dryer, cotton and heated air initially enter the tower dryer through an inlet, located proximate to the top of the tower casing. The heated air carries the cotton through the sinuous passage in the dryer to the outlet. As the cotton, which may have an initial moisture content of between about 15% to 20%, passes through the dryer, moisture is progressively driven from the cotton until the cotton exits the dryer with a moisture content as low as 0%. The desired range of moisture content for cotton before cleaning is about 51/2% to 61/2%.
After removing the trash from the seed cotton, the cotton is now substantially free of seeds and trash. At this stage the cleaned cotton is referred to as cotton lint. After drying the cotton to facilitate cleaning of the cotton, it usually will have a moisture content lower than 8%. It often will have moisture content of about 3 or 4%. This level of moisture content facilitates cleaning, but it is lower than the ideal moisture content for processing the cotton through the batting stage and for the final product.
It is lower than desired because low moisture content causes mechanical problems and stress on the cotton bale press tamper and ram. Added moisture allows the cotton to flow through the battery condenser more easily, as cotton too dry and fluffy can cause mechanical problems, and relieves the strain on the cotton bale press tramper and the cotton bale press ram. Higher moisture contents also reduces billowing of the cotton when the cotton bale is opened; billowing increasing the processing cost of making cotton fibers into fabric.
Typical methods used to add moisture to cotton are described in U.S. Pat. No. 4,140,503 granted to Vandergriff and U.S. Pat. No. 4,103,397 granted to Jackson. These patents show systems that add moisture to the cotton while the cotton lint is within a battery condenser or after the cotton has been condensed. One of the problems with these and other conventional systems is that they do not raise the moisture level sufficiently if the initial moisture content of the cotton is very low. Further, the humid air for these systems is added to a structure that is at a relatively low temperature. Because of this low temperature, the humid air condenses on the parts of the structure. Water condensed on the surfaces that cotton comes into contact with will impede the progress of the cotton, making the cotton stick to the areas where the water has condensed. Also, these systems do not do a good job of regulating the moisture content of the cotton, thereby allowing the moisture of the content to vary from the ideal post-cleaning moisture content of 8%.